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Double-sided VRay materials display incorrect shading in viewport after starting/stopping IPR.
Steps to reproduce:
1. Create a plane.
2. Apply VRayMtl with a basic color.
3. Rotate plane so the backside is facing view (normals facing away from view).
4. Make sure double-sided is checked in material (may have to toggle off/on to see change in viewport).
5. Start/Stop IPR.
You should see the material on the backside will turn black. You can get the double-sided material to work again by either toggling the "Double-sided" checkbox or by simply toggling the "Show Shaded Material in Viewport" button on the material editor. But once you start IPR again it'll revert back to black. Regular rendering does not cause this issue. In fact, it corrects the double-sided materials in the viewport after render is completed. But, starting IPR will break it again. Standard 3ds Max materials don't seem to have this issue.
One thing to note is the material isn't actually missing or completely black. If you rotate the view or object to a glancing angle, you'll see the material start to appear. The shading looks to be reversed. See image below for example.
Steps to reproduce:
1. Create a plane.
2. Apply VRayMtl with a basic color.
3. Rotate plane so the backside is facing view (normals facing away from view).
4. Make sure double-sided is checked in material (may have to toggle off/on to see change in viewport).
5. Start/Stop IPR.
You should see the material on the backside will turn black. You can get the double-sided material to work again by either toggling the "Double-sided" checkbox or by simply toggling the "Show Shaded Material in Viewport" button on the material editor. But once you start IPR again it'll revert back to black. Regular rendering does not cause this issue. In fact, it corrects the double-sided materials in the viewport after render is completed. But, starting IPR will break it again. Standard 3ds Max materials don't seem to have this issue.
One thing to note is the material isn't actually missing or completely black. If you rotate the view or object to a glancing angle, you'll see the material start to appear. The shading looks to be reversed. See image below for example.
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